Underscores in user names and security

There seems to be a security problem when using user names with underscores. When I visit lj_abuse.livejournal.com no journal entries are displayed. However, visiting lj-abuse.livejournal.com or www.livejournal.com/users/lj_abuse I see all my protected entries just like they are supposed to be (I'm logged in). I should be able to see them when using lj_abuse.livejournal.com, right? I believe this means there's some type of bug that affects the translation of usernames from "_" to "-" or vice versa.